The research objective is to examine the development of empathy and prosocial behavior in relation to progressive differentiation of self and other in the second year of life. Data on children's empathic capabilities are taken from mothers' systematic observations of their children's responses to naturally occurring emotional incidents in the home environment. Understanding of self and others is assessed by a Self Recognition Scale (children's reactions to their own mirror image) and an Agent Use Scale (understanding of other persons as independent agents in the context of pretend play). An Objective Permanence Scale is also administered as a standard measure of cognitive development in the sensorimotor period. Twenty children are studied from 10 months of age until two years. Data collection is complete and analysis is under way.